Environmental awareness in cruise ship business and among passengers lead to increased need to minimize the emissions to the environment. Scrubber units for scrubbing exhaust gas from internal combustion piston engines have been used on marine vessels to some extent for reducing the exhaust gas emission to the atmosphere. Exhaust gas is led into the scrubber unit in which a scrubbing medium, such as an alkaline washing solution, is sprayed into the exhaust gas, whereby the alkaline components react with acidic components of the exhaust gas. The scrubbing medium is sometimes supplied from a so-called process tank. The scrubbing medium absorbs SO2, heat and other components from the exhaust gas flow. Before the scrubbed exhaust gas is discharged to the atmosphere, it may be led through a droplet separator arranged before the stack of the vessel. Due to e.g. stricter environmental regulations so called two-stage or multi-stage scrubber units have been developed. In such scrubber units, scrubbing medium is sprayed into the exhaust gas flow at two or several stages.
As examples of such scrubber units it is referred to publications WO 2007/045721 A1 and WO 2012/113977 A1. WO 2007/045721 A1 discloses a method of and an arrangement for treating the exhaust gases of a large supercharged internal combustion engine, especially a diesel engine, in a system, in which the exhaust gases from the engine are conducted to an exhaust gas scrubber to be washed and cooled at least mainly by water.
WO 2012/113977 A1 discloses a method of treating exhaust gas in a two-stage scrubber system of a marine vessel with a water based solution, in which the exhaust gas is treated in the first scrubber unit by means of sea water based scrubbing medium and that the exhaust gas is treated in the second scrubber unit by means of fresh water based scrubbing medium.
Document US2010206665 A1 discloses a muffler for engines in oil-field applications. Document discloses spraying nozzles for spraying water mist and flushing ports for delivering water into the muffler.
Document GB 2332631 A discloses an apparatus for removing carbon particulate from the exhaust gas stream of an internal combustion engine where oil is injected into the exhaust gas which is then vaporized and further cooled down such that condensation occurs to droplets of oil within which the particulates are suspended.
For practical reasons the scrubber unit is very difficult, if not impossible, to be positioned as the latest component in the exhaust gas system in a marine vessel, the exhaust gas system has an end duct portion leading downstream from the scrubber unit to the funnel of the vessel. Now, it has been discovered that operation is a circumstances is not of satisfactory and therefore it is an object of the invention to provide a scrubber unit in which the performance is considerably improved compared to the prior art solutions.